It is well-known that the Arab philosophers of the Aristotelian tradition, like some of their Alexandrian predecessors, attached rhetoric and poetics to logic, and supported this inclusion by the idea that the principal poetic procedure - that is, essentially, metaphor - is a kind of syllogism: the poetic syllogism. However, until now, no texts prior to those of Avicenna had been identified which render the structure of this syllogism explicit. In the present contribution, we present and translate a passage from al-Fārābī which shows that for him, the poetic syllogism is an incorrect syllogism of the second figure - a different interpretation from that which will be given by Avicenna.